Study of Direct Photon plus Jet production in CMS Experiment at \sqrt{s}=14 TeV

Abstract

We present simulation results of $\gamma$ + Jet analysis using CMS (Compact Muon Solenoid) Object-Oriented software at the Large Hadron Collider (LHC) center of mass energy $\sqrt{s}$=14 TeV. The study of direct photon production helps in validating the perturbative Quantum Chromodynamics (pQCD) and providing information on the gluon distribution in the nucleons. Direct photon processes also constitute a major background to several other Standard Model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the new energy regime. In this work, we have done a detailed study of the GEANT4 simulated $\gamma$ + jet events generated with Pythia, and the related background processes. Isolation cuts have been optimized for direct photon which improves the signal over background ratio by $\sim 25$ as compared to previous studies done in CMS. The inclusion of a large $\Delta \varphi$ cut between the photon and the leading jet at $40^0$ in the analysis leads to a further increase of $\sim 15$ in S/B, thus giving an overall gain of $\sim 42$ in S/B ratio.

20 Pages, 13 Figures. Accepted in European Journal of Physics C

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• String Physics at the LHC
• Prompt photon production in photoproduction, DIS and hadronic collisions
• Particle Phenomenology of Gravitational Events at the TeV Scale
• QCD Physics Potential of CMS
• Manifestations of String Theory in Astrophysical Data and at the LHC